Sealants have been commonly employed for meeting the sealing and bonding requirements in fabrication of windows, doors, recreational vehicle and other manufactured home appliances to reinforce the structural strength of the substrate on which it is applied.
Sealant compositions that are available today are mainly based on mono chemistries like silicone, polyurethane, acrylic, and the like. However, unfortunately, these compositions suffer from a number of disadvantages. For example, many of these sealant compositions are being hygroscopic and may not possess the desired adhesion characteristics, when used in connection with some varied substrates, particularly in high moisture environments. Thus, the commercially available sealants have certain drawbacks such as inadequate shelf life due to hygroscopic nature, limited thermal stability, void formation owing to evolution of carbon dioxide during the curing process, requirement of expensive raw materials, requirement of high temperature, high shrinkage rate and release of acid volatiles which cause cross contamination problems on substrates.
For instance, sealants based on isocyanate-terminated polyurethanes are incompatible for long-term packaging and storage due to their short shelf life, in that i.e., the prepolymers that tend to cure in situ during storage. Also, isocyanate based sealants suffer from the drawback of limited thermal stability. Other commonly employed sealants are based on silicone polymers which are characterized by strong bonding, adhesion and mechanical properties. Silicone sealants generally have desirable properties and yield seals of high quality that perform well under many conditions. Unfortunately, silicone sealants often require expensive raw materials. Also, silicone sealants often do not possess the desired adhesion characteristics when used in connection with certain substrates, particularly in high moisture environments. Further, as many silicone precursors are hygroscopic in nature, silicones tend to form lumps or based on cure clarity, release acidic or basic by product, which corrode or otherwise contaminate the substrate.
Thus, a there is a need for a composition which will materially alleviate the difficulties associated with the traditional sealants and provide superior mechanical and bonding properties with a rapid build of green strength as compared with commercially available sealants. Further, there is a need for a sealant composition that will have adequate shelf life.
Further, there also exists a need for a self-leveling sealant that will flow or “level out” to provide a substantially uniform coating by filling recessions and other minor imperfections in the substrate. Such a self-leveling sealant composition is particularly well suited for application to a substantially horizontal surfaces to seal mechanically fixed joints such that with rapid build of green strength and upon quick curing elastic solid polymeric mass a sealant is created that will meet sealant requirements of window, door, recreational vehicle and other manufactured home appliances.